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Top Forums Shell Programming and Scripting any way to speed up calculations in bash script Post 302276886 by cfajohnson on Thursday 15th of January 2009 12:08:39 AM
Old 01-15-2009
Quote:
Originally Posted by npatwardhan
is there any way i can speed it up?

Don't call the external command 21,000 times. Pipe your calculations to a single instance of it.

And I would use awk rather than bc.

Code:
while [ $j -lt $outer ];do
  i=0
  while [ $i -lt $count1 ];do
    printf "%f\n" "${ARRAY1[k]} - ${ARRAY2[j]}"
    i=$(( $i + 1 ))
    k=$(( $k + 1 ))
  done 
  echo
  j=$(( $j + 1 ))
done | awk '/^$/ { print; next }
{ printf "%.1f," $1 - $2 }
'  > "$count.diff"

If you are processing the entire arrays:

Code:
for a in "${ARRAY1[@]}"
do
  printf "%f $a\n" ${ARRAY2[@]}
  echo
done | awk '/^$/ { print; next }
{ printf "%.1f,", $1 - $2 }
'

 

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RBASH(1)						      General Commands Manual							  RBASH(1)

NAME
rbash - restricted bash, see bash(1) RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow- ing are disallowed or not performed: o changing directories with cd o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV o specifying command names containing / o specifying a filename containing a / as an argument to the . builtin command o specifying a filename containing a slash as an argument to the -p option to the hash builtin command o importing function definitions from the shell environment at startup o parsing the value of SHELLOPTS from the shell environment at startup o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators o using the exec builtin command to replace the shell with another command o adding or deleting builtin commands with the -f and -d options to the enable builtin command o using the enable builtin command to enable disabled shell builtins o specifying the -p option to the command builtin command o turning off restricted mode with set +r or set +o restricted. These restrictions are enforced after any startup files are read. When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. SEE ALSO
bash(1) GNU Bash-4.0 2004 Apr 20 RBASH(1)
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